1. Field of the Invention
The present invention is directed to a drive shaft damper assembly structured to be installed on a drive shaft of a vehicle while the drive shaft remains installed on the vehicle. The present drive shaft damper assembly further includes a bushing assembly structured to permit a user to “tune” the drive shaft to compensate for inherent manufacturing irregularities which may cause a drive shaft to rotate offset from its central axis.
2. Description of the Related Art
Most automobiles manufactured today include a two piece drive shaft joined together using constant velocity (“C.V.”) joints approximately midway along its length. More in particular, the C.V. joints are structured to compensate for minor misalignment between the separate pieces of the shaft as well as to compensate for the vibration to which the drive shaft is exposed during operation. In addition to the C.V. joints which join the separate portions of the drive shaft together, most automobiles are also equipped with a damper mechanism including a center support around at least a portion of one of the drive shaft members, wherein the center support includes an annular bushing which serves to cushion or dampen the vibrational forces exerted on the vehicle via rotational force generated of the drive shaft. As originally manufactured, the damper mechanism typically has an annular rubberized bushing or damper member which completely encircles and is fixedly attached to an outer bearing race, while a corresponding inner bearing race is securely affixed to a portion of the drive shaft itself, a plurality of ball bearings being operatively disposed therebetween. The outer periphery of the annular bushing is affixed to the inside of the center support which is secured to the underside of the vehicle itself. As will be appreciated, the continuous annular configuration of the bushing or damper member allows for both compression and tension forces to be exerted on the annular bushing. More in particular, the annular bushing can accommodate both tension and compression forces exerted thereon as a result of movement of the drive shaft from its central longitudinal axis of rotation. That is to say, when the drive shaft rotates offset from it central longitudinal axis of rotation, such as occurs due to inherent manufacturing irregularities and/or the set up of resonant frequencies, it will exert a compression force on one portion of an annular bushing, while a substantially equal and opposite tension force will be disposed approximately 180° degrees from the point of the compressive force on the annular bushing. As such, the opposing tension and compression forces act together to reposition the drive shaft and minimize the deviation of its rotation from its central longitudinal axis.
It has been observed that the annular bushing of the central support such as described above tends to fail after even moderate use in many vehicles, namely, in the range of about forty-thousand to sixty-thousand miles of operation. Of course, most vehicles manufactured today are designed to operate well over one hundred thousand miles, if not several hundred thousand miles. Therefore, it is common for the owners of many vehicles to have to replace the annular bushing several times over the useful life of the vehicle. Presently, in order to replace the annular bushing, the central support, annular bushing, and drive shaft bearing must all be removed from the drive shaft and replaced, thus requiring at least partial removal of the drive shaft from the vehicle itself, which requires significant time, labor, and expense. In many cases, the C.V. joints must be disassembled to remove the drive shaft, thereby requiring replacement of the same, adding further time and expense to the process. As will be appreciated, this is a very labor intensive procedure and, when the cost of the replacement parts are taken into account, the entire process can easily cost upwards of thousands of dollars per occurrence. In addition to this considerable expense, the owner of the vehicle is often without use of the vehicle for an extended period of time while the drive shaft is removed, replacement parts are ordered, and the drive shaft, annular bushing, and, in many cases, the C.V. joints, are reinstalled onto the vehicle.
In view of the time and expense required to resolve this problem, alternatives have been sought to replace the annular bushing of the central support without requiring disassembly and removal of the drive shaft or C.V. joints from the vehicle. Common to these alternatives is that at least a portion of an annular bushing is cut or split in order to allow placement over the outer bearing race of the drive shaft bearing mounted to the drive shaft, which remains installed on the vehicle. One such alternative provides an annular bushing which is split into two semicircular bushing portions which are positioned around the bearing assembly and are retained in place by an outer clamp. While this structure eliminates the need for removal of the drive shaft assembly from the vehicle, it introduces an inherent operational defect which negates at least one aspect of the intended purpose of the annular bushing itself. Specifically, as noted above, the original continuous annular bushing is structured such that substantially equal and opposing tension and compression forces are exerted on opposite portions of the continuous annular bushing by the drive shaft, because the annular bushing is fixedly attached to both the drive shaft bearing and the center support. As a result, these forces serve to act together to reposition the drive shaft into alignment with its central longitudinal axis of rotation.
As will be readily appreciated, however, when a continuous annular bushing is cut into two or more portions and positioned around the drive shaft bearing without being securely affixed to the drive shaft bearing as well as to the outer clamp, when the drive shaft exerts a compressive force on one portion of the split annular bushing, there is no longer a substantially equal and opposite tension force exerted on the other portion of the annular bushing opposite the point of compression. As such, a split annular bushing simply cannot serve the intended function of repositioning the drive shaft into alignment with its central longitudinal axis of rotation.
As such, it would be beneficial to provide an improved bushing assembly which may be mounted around a drive shaft while the drive shaft remains installed on a vehicle. More in particular it would be helpful for such an improved bushing assembly to be responsive to both compression and tension forces exerted by the drive shaft, such that the forces act together to reposition the drive shaft into alignment with its central longitudinal axis of rotation. Further, it would be beneficial for such an improved bushing assembly to allow for “tuning” of the drive shaft to minimize the set up of resonance frequencies which can result in unnecessary and potentially harmful or dangerous vibration of a vehicle during operation. A further benefit would be realized by providing an improved drive shaft damper assembly which permits replacement of individual bushing members without requiring removal of the entire drive shaft damper assembly from the drive shaft of the vehicle.